Noise reducer for gun



1959 w. J. JARRETT NOISE REDUCER FOR GUN Filed Jan. 11, 1956 INVENTOR. \hgllium 111112 2211 1P. Z. W M 62w. Qw-

NOISE REDUCER FOR GUN William J. Jarrett, Springfield, Mass., assignor to the United States of America as represented by the Secretary of the Army Application January 11, 1956, Serial No. 558,593

1 Claim. (Cl. 89-14) (Granted under Title 35, U. S. Code (1952), sec. 266) V: (gKRT) 1/2 where Vfihe velocity of sonic propagation in propellant gas in feet per second, g=the gravitational constant 32.2 foot pounds per second per'second, R the universal gas constant (119), and T=the temperature in degree centigrade.

If the process is assumed to be adiabatic with K=l.246, the value of V is expressed by The barrel of a gun is a tube or pipe with a closed end having the source of vibration disposed at the open end since the vibrations are set up as the gases leave the barrel. The equation of the fundamental frequency of resonance of the tube is f, in cycles per second.

The barrels of usual firearms vary from two inches for a pistol to 36 inches for a rifle, therefore,

4 XE =l2,080 0.1. S. for 2" barrel =675 o. P. s. for 36 barrel The fundamental frequency, therefore, varies roughly between frequencies of 675 and 12,080 cycles per second which are within the sonic range.

Since the whole amount of discharged gas escapes from the gun to the atmosphere, the volume of sound thus created often causes distress to people confined in a closed space with a gun being fired, and in the open, permits the discharge of the gun to be heard at great distances to disclose the location of the gun.

Silencers for guns have been developed but the silencers now existing are heavy, cumbersome attachments for the barrels with chambers and labyrinths or the like for reducing the pressure of the discharged gases from the guns, and ports to increase the area of discharge of the gases from the barrels.

Z,858,'i"8 Patented Jan. .13, 1959 His an object of my invention to produce a light compact device to reduce the audible noise of discharge of a machine operated by a gas having a high acoustic velocity.

Another object of my invention is to provide a noise reducer to limit the audible noise of discharge of a gun.

A further object of my invention is to provide a noise reducer to limit the sonic vibrations in the gas emitted from a gun.

A still further object of my invention is to provide a gun with a device including a discharge gas chamber and ports therein for escape of gases from the gun at supersonic frequencies of vibration.

Yet a further object of my invention is to provide a gun with a barrel extension including an entry chamber for leakage of discharge gases around a projectile, an

exit chamber having substantially the bore of the gun and an intermediate chamber having a bore greater than the bores of the entry and exit chambers, and gas exhaust ports. 3

Other aims and objects ofmy invention will appear from the following explanation thereof.

In carrying out my invention a barrel extension for attachment to a gun includes an aperture with a plurality of chambers including an entry chamber with a bore substantially larger than the diameter of a projectile for leakage of gases therearound, an intermediate chamber having ports with sharp edges for escape of discharge gases therefrom, and an exit chamber with a bore substantially equal to the bore of the gun barrel. The intermediate chamber is provided with a bore greater than the bores of the entry and exit chambers and a length required to resonate supersonic vibrations.

For a more complete understanding of my invention, reference is directed to the following description and the accompanying drawing in which:

Fig. 1 is an elevation, partly in section of a portion of a gun incorporating an embodiment of my invention, with the projectile about to enter the intermediate chamber;

Fig. 2 is a view similar to Fig. 1 with the projectile leaving the gun;

Fig. 3 is a muzzle end view of the barrel extension; and

Fig. 4 is a perspective view of the barrel extension.

Accordingly, a gun 12 having a barrel 14- for discharge of projectiles 15 therethrough is provided with a barrel extension 16 having a body 18 secured to gun 12 by a nut 20.

Body 18 is provided with a first chamber 24 and a second chamber 28 of larger diameter extending forwardly therefrom. The front end of second chamber 28 is terminated by an annular flange 27 through which there is provided an axial aperture 26.

Front chamber 24 is disposed immediately forward of the muzzle end of barrel 14 and has a diameter slightly larger than that of the projectiles 15 so that some of the gases propelling the projectiles forwardly may escape thereby into second chamber 28 before the entry of the projectiles thereinto. Second chamber 28 has a predetermined length and extending laterally from the front end thereof is a pair of diametrically opposed mouth portions 30. The outside of body 18, immediately forward of the mouth portions 30, is cut away to form arcuate surfaces 33 concentric to body 18 with such surfaces having a radius slightly smaller than that of second chamber 28. The junctions of the annular surfaces 33 with the inside face of flange 27 form a right angular edge 32 which lies in the path of the gases expelled forwardly from second chamber 28 to cause the discharge gases to vibrate in the same manner as the passage thereof through a whistle. The frequencies of the vibrations are determined by the length of second chamber 28 and, therefore, the length of such chamber is predetermined as .8

inch. wher a hereinafter. xpla ned the r q enc at which the discharge gases vibrate is above the limit of human audibility. Aperture 26 has a diameter approximatelvthe. sameas thaLof; projectiles. 1 5 so. that when such projectiles are passingtherethrough the. discharge gases are directed entirely, out through the mouth 30.

The value of f, the frequency of vibration intthegas discharged from aclosed pipe is expressed by Where f=cycles per second, V=the velocity of sonic propagation in air in feettper second, and l=the length of the pipe in feet,

The frequency of sounglin the gases-escapingfrom ports 30 in cycles per second with-a, chamber length of .8 inch, therefore, is

= 20,000 C; P; S.

This frequency is supersonic since the upper limit of 61 entry chamber24' determines the degree of the attenuation. 7 I

Although a particular embodiment of the invention has been described in detail herein, it is evident that many variations may be devised within the spirit and scope thereof and the-following claim is intended to include such variations.

I claim:

An attachment for the muzzle end of a firearm barrel to reduce thenoiserproducedby the discharge of gases therefrom, said attachment including the combination of a body provided with a chamber having a diameter larger thanthat-of the bore-of the barrel, an annular flange provided with a rear face and disposed at the front end of said chamber, said flange having an aperture therethrough in axial alignmentwith the barrel, a pair of mouth portions extending radially outward from said chamber rearwardly of said flange for the discharge of the gases, cutout portions extendingforwardly. insaid body from said mouth portions, arcuate surfaces formed on said flange. by said cutout portions, arcuate edges formed at the junctions of said arcuate surfaces with said rear face, said arcuate surfaces having a radius smaller than that of said chamber to locate said edges in the forward path of' the, gasesto setup vibrations therein when discharged through said mouth portions, andsaid chamber having a predetermined length for producing the vibrations at a frequency higher than that of audible sound.

References Cited 'in the file of this patent UNITED STATES PA'r-JTEIITS 1,143,814 De Vries June 22, 1915 FOREIGN PATENTS 314,842 Germany Nov. 29, 1917 270,629 Italy Jan. 15, 1930 

